Balloon catheter having a flexible distal end

ABSTRACT

A catheter having an elongated shaft with a proximal end, a distal end, and at least one lumen, and a distal portion of the shaft being at least in part within an outer sheath having a wedge-shaped distal end. In one embodiment, the outer sheath around the distal end of the shaft is the distal skirt section of the balloon. In an alternative embodiment, the outer sheath is a sleeve member having at least a portion located distal to the distal end of the balloon.

BACKGROUND OF THE INVENTION

This invention generally relates to catheters, and particularlyintravascular catheters for use in percutaneous transluminal coronaryangioplasty (PTCA) or for the delivery of stents.

In percutaneous transluminal coronary angioplasty (PTCA) procedures aguiding catheter is advanced in the patient's vasculature until thedistal tip of the guiding catheter is seated in the ostium of a desiredcoronary artery. A guidewire is first advanced out of the distal end ofthe guiding catheter into the patient's coronary artery until the distalend of the guidewire crosses a lesion to be dilated. A dilatationcatheter, having an inflatable balloon on the distal portion thereof, isadvanced into the patient's coronary anatomy over the previouslyintroduced guidewire until the balloon of the dilatation catheter isproperly positioned across the lesion. Once properly positioned, thedilatation balloon is inflated with inflation fluid one or more times toa predetermined size at relatively high pressures so that the stenosisis compressed against the arterial wall and the wall expanded to open upthe vascular passageway. Generally, the inflated diameter of the balloonis approximately the same diameter as the native diameter of the bodylumen being dilated so as to complete the dilatation but not overexpandthe artery wall. After the balloon is finally deflated, blood flowresumes through the dilated artery and the dilatation catheter and theguidewire can be removed therefrom.

In such angioplasty procedures, there may be restenosis of the artery,i.e. reformation of the arterial blockage, which necessitates eitheranother angioplasty procedure, or some other method of repairing orstrengthening the dilated area. To reduce the restenosis rate ofangioplasty alone and to strengthen the dilated area, physicians nownormally implant an intravascular prosthesis, generally called a stent,inside the artery at the site of the lesion. Stents may also be used torepair vessels having an intimal flap or dissection or to generallystrengthen a weakened section of a vessel or to maintain its patency.Stents are usually delivered to a desired location within a coronaryartery in a contracted condition on a balloon of a catheter which issimilar in many respects to a balloon angioplasty catheter, and expandedwithin the patient's artery to a larger diameter by expansion of theballoon. The balloon is deflated to remove the catheter and the stentleft in place within the artery at the site of the dilated lesion. Seefor example, U.S. Pat. No. 5,507,768 (Lau et al.) and U.S. Pat. No.5,458,615 (Klemm et al.), which are incorporated herein by reference.

An essential step in effectively performing a PTCA procedure is properlypositioning the balloon catheter at a desired location within thecoronary artery. To properly position the balloon at the stenosedregion, the catheter shaft must be able to transmit force along thelength of the catheter shaft to allow it to be pushed through thevasculature. However, the catheter shaft must also retain sufficientflexibility to allow it to track over a guidewire through the oftentortuous vasculature. Additionally, the catheter also must have goodcrossability (i.e., the ability of the catheter distal end to crossstenosed portions of the vascular anatomy).

Conventional intravascular catheters have commonly included a softdistal tip to prevent or minimize injury to the vessel duringadvancement of the catheter therein. One difficulty has been forming aconnection between the soft tip and the catheter which is sufficientlystrong to prevent disengagement of the soft tip or kinking at thejunction between the soft tip and catheter shaft. Additionally, it isnecessary to balance the strength of the connection between the soft tipand the catheter shaft with the need to minimize the stiffness of thedistal end of the catheter. Minimizing the stiffness of the distal endof the catheter results in improved maneuverability of the catheter.

Accordingly, it would be a significant advance to provide a catheterwith a soft tip having improved performance. This invention satisfiesthese and other needs.

SUMMARY OF THE INVENTION

The invention is directed to a catheter having an elongated shaft with aproximal end, a distal end, and at least one lumen, and a distal portionof the shaft being at least in part within an outer sheath having awedge-shaped distal end.

In a presently preferred embodiment, the catheter is a balloon catheterwith a balloon on a distal shaft section, having an interior in fluidcommunication with the at least one lumen of the catheter shaft. Aballoon catheter of the invention generally comprises an elongated shafthaving a proximal shaft section, a distal shaft section, an inflationlumen extending within the proximal and distal shaft sections, and aguidewire receiving lumen extending at least within the distal shaftsection, and an inflatable balloon on the distal shaft section with aninterior in fluid communication with the inflation lumen. The balloontypically has a proximal skirt section and a distal skirt sectionsealingly secured to the shaft, and an inflatable section therebetween.In a presently preferred embodiment, the shaft comprises an outertubular member defining the inflation lumen, and an inner tubular memberdefining at least a portion of the guidewire receiving lumen. However, avariety of suitable shaft designs may be used including dual-lumen typeshafts. The balloon catheter of the invention may comprise a variety ofsuitable balloon catheters, including coronary and peripheral dilatationcatheters, stent delivery catheters, drug delivery catheters, and thelike.

In one embodiment, the distal skirt section of the balloon forms thewedge-shaped outer sheath around the distal end of the shaft. In analternative embodiment, the outer sheath is a sleeve member having atleast a portion located distal to the distal end of the balloon. Thewedge-shaped distal end has an angled (i.e., truncated) end formed by adistal leading face which is oriented at an angle of about 30 to about60 degrees, more preferably about 45 to about 55 degrees relative to thelongitudinal axis of the shaft. The wedge-shaped end of the outer sheathprovides distally increasing flexibility for a smooth transition instiffness along the distal end of the catheter, to improve handling andperformance and minimize kinking. In a presently preferred embodiment,the outer sheath has a proximal cylindrical section proximal to thewedge-shaped distal end. The proximal section of the outer sheathpreferably has a circular or oblong transverse cross sectional shape,although it can have a variety of suitable shapes.

In a presently preferred embodiment, a distal tip member having at leasta portion distal to the inner tubular member forms the distal end of theshaft, and defines a distal portion of the guidewire lumen in fluidcommunication with the portion of the guidewire lumen defined by theinner tubular member. The distal tip member provides improvedflexibility at the shaft distal end for improved maneuverability.However, in an alternative embodiment, the distal tip member is omitted,and the distal end of the inner tubular member defines the distal end ofthe shaft. The distal tip member is typically softer and more flexiblethan the inner tubular member. In one embodiment, the distal tip memberis formed of a material having a lower Shore Durometer hardness than apolymeric material forming at least part of the inner tubular member, toprovide a soft, flexible, atraumatic distal end, which consequentlyprovides improved catheter maneuverability and decreases the risk ofdamage to the patient's vessel during advancement of the cathetertherein. The Shore Durometer hardness of the polymeric material formingthe tip,member is typically about 40 D to about 70 D, preferably about55 D to about 65 D. In a presently preferred embodiment, the distal tipmember is formed of a polyurethane, including a polyurethane copolymersuch as PELLETHANE (a polyester polyurethane copolymer), available fromDow Plastics. However, the distal tip member may be formed of a varietyof suitable materials, including polyolefin based copolymers such as apolyethylene based adhesive polymers such as an ethyleneacrylic acidcopolymer which is sold commercially as PRIMACOR by Dow Chemical Co.,and polyether block amide polymer such as PEBAX (available fromAutochem).

In a presently preferred embodiment, the wedge-shaped outer sheath isaround a distal end of the inner tubular member and at least a proximalend of the distal tip member. However, a variety of suitableconfigurations may be used in which the location of the distal end ofthe shaft relative to the outer sheath varies. For example, in oneembodiment, the distal end of the shaft is distal to the distal end ofthe wedge-shaped outer sheath, to provide an atraumatic leading distalend. However, in an alternative embodiment, the distal end of thewedge-shaped outer sleeve is distal to the distal end of the shaft, toprovide enhanced support at the distal tip for improved tensile strengthand a decrease in the distance between the distal end of the catheterand the proximal end of the balloon skirt section. In the embodimenthaving a distal tip member distal to the inner tubular member, thedistal end of the inner tubular member is preferably located proximal tothe wedge-shaped distal end of the outer sheath (i.e., proximal to theproximal end of the distal leading face of the wedge-shaped distal endof the outer sheath), although it may alternatively be located distal tothe proximal end of the wedge-shaped distal end of the outer sheath, orproximal or distal to the outer sheath, depending on the desiredperformance characteristics of the catheter.

The outer sheath has at least a section secured to the inner tubularmember and/or the distal tip member. In the embodiment in which theouter sheath is the distal skirt section of the balloon, at least asection of the balloon distal skirt section is bonded, for example byfusion or adhesive bonding, to the shaft. In a presently preferredembodiment, the proximal-most portion of the distal skirt section of theballoon is typically not bonded to the inner tubular member or distaltip therein. The section of the outer sheath bonded to the underlyingsection of the shaft typically flows and fuses together with thepolymeric material forming at least an outer surface of the underlyingsection of the shaft (i.e., the inner tubular member and/or distal tip),so that the bonded outer surface of the outer sheath typically has adistally tapering outer diameter.

The catheter of the invention has excellent maneuverability andcrossability due to the distal end of the catheter having a wedge-shapedouter sheath around the distal end of the shaft. The wedge-shaped outersheath provides gradually decreasing flexibility at the catheter distalend, for improved handling and performance. Moreover, in the embodimenthaving a soft distal tip forming the distal end of the shaft, thecatheter has excellent tensile strength at the distal tip attachment,without disadvantageously increasing the stiffness or profile of thedistal end of the catheter. These and other advantages of the inventionwill become more apparent from the following detailed description andexemplary drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view, partially in section, of a ballooncatheter which embodies features of the invention.

FIG. 2 is a transverse cross sectional view of the catheter shown inFIG. 1, taken along line 2—2.

FIG. 3 is a transverse cross sectional view of the catheter shown inFIG. 1, taken along line 3—3.

FIG. 4 is a transverse cross sectional view of the catheter shown inFIG. 1, taken along line 4—4.

FIG. 5 is a transverse cross sectional view of the catheter shown inFIG. 1, taken along line 5—5.

FIG. 6 is an enlarged, longitudinal cross sectional view of analternative embodiment of the catheter of FIG. 1, having a balloondistal skirt section with a tapering outer surface.

FIG. 7 is an enlarged, longitudinal cross sectional view of an alternateembodiment of a catheter embodying features of the invention, having awedge-shaped sleeve member around the distal end of the shaft.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an over-the-wire balloon catheter 10 embodyingfeatures of the invention. Catheter 10 generally comprises an elongatedcatheter shaft 11 having a proximal end, a distal end, a proximal shaftsection 12, a distal shaft section 13, an outer tubular member 14, andan inner tubular member 15. Inner tubular member 15 defines a guidewirelumen 16 adapted to slidingly receive a guidewire 17, and the coaxialrelationship between outer tubular member 14 and inner tubular member 15defines annular inflation lumen 18, as best shown in FIG. 2,illustrating a transverse cross section of the catheter of FIG. 1, takenalong line 2—2. An inflatable balloon 19 is disposed on the distal shaftsection 13, having a proximal skirt section 20 sealingly secured to thedistal end of outer tubular member 14, and a distal skirt section 21sealingly secured to the distal end of inner tubular member 15, so thatits interior is in fluid communication with inflation lumen 18. Anadapter 31 at the proximal end of the shaft is configured to provideaccess to guidewire lumen 16, and to direct inflation fluid through arm30 into inflation lumen 18. FIG. 1 illustrates the balloon 19 inflated.The distal end of catheter may be advanced to a desired region of apatient's body lumen in a conventional manner, and balloon 19 inflatedto perform a procedure, and the balloon deflated, and the catheterrepositioned or withdrawn from the body lumen. FIG. 3 illustrates atransverse cross section of the catheter of FIG. 1, taken along line3—3.

The catheter 10 has a wedge-shaped outer sheath, which in the embodimentof FIG. 1 is the distal skirt section 21 of the balloon. The tapereddistal leading face or edge forming the wedge-shape of the distal skirtsection 21 tapers at an angle relative to the longitudinal axis of theshaft. In the embodiment of FIG. 1, the angle is about 55 degreesrelative to the longitudinal axis of the shaft, although alternativeangles can be used depending on the materials forming the distal end ofthe catheter and the desired performance of the catheter. FIGS. 4 and 5illustrate transverse cross sections of the catheter of FIG. 1, takenalong lines 4—4, and 5—5, respectively. Although illustrated with acircular transverse cross sectional shape in the figures, the distalskirt section 21 and underlying shaft section can have a variety ofsuitable shapes including oblong, and the like. The balloon distal skirtsection 21 has a proximal section which is continuous around the shafttherein, as best illustrated in FIG. 4. In contrast, at the wedge-shapeddistal leading face, the balloon distal skirt section 21 extends onlypartially around the shaft therein, as best illustrated in FIG. 5.

The distal leading face of the wedge-shaped distal skirt section 21 hasa proximal end 22 and a distal end 23 and a length extending from theproximal end 22 to the distal end 23 thereof. The distal skirt section21 has a cylindrical section proximal to the wedge-shaped distal leadingface. Preferably, the length of the wedge-shaped distal leading face isabout 20 to about 75% of the length of the distal skirt section 21, andin one embodiment is about 2.5 to about 4 mm.

In the embodiment of FIG. 1, the distal end of the shaft is locateddistal to the distal end of the wedge-shaped distal skirt section 21. Adistal tip member 24 forms the distal end of the shaft. In theembodiment of FIG. 1, the wedge-shaped distal skirt section 21 surroundsa distal end of the inner tubular member 15 and a proximal end of thedistal tip member 24. The distal tip member 24 defines a distal portionof the guidewire lumen 16 in fluid communication with the portion of theguidewire lumen 16 defined by the inner tubular member 15. In theembodiment of FIG. 1, the distal tip member 24 extends from a locationproximal of the proximal end 22 of the wedge shaped distal leading face,to a location distal of the distal end 23 of the wedge shaped distalleading face, so that the distal tip member 24 extends through theangled end of the wedge-shaped distal skirt section 21.

In the embodiment of FIG. 1, the distal tip member 24 has a proximal endspaced distally apart from the inner tubular member 15, forming a gaptherebetween which is surrounded by the cylindrical proximal portion ofthe balloon distal skirt section 21. Although illustrated with a gapbetween the inner tubular member 15 and the distal tip member 24, avariety of suitable junctions between the distal tip member and theinner tubular member may be used including lap and butt joints.Additionally, in an alternative embodiment, tip member 24 is omitted, sothat the inner tubular member 15 would extend in place of the tip member24 through the angled end of the wedge-shaped distal skirt section 21.

The wedge-shaped distal skirt section 21 of the balloon 19 is bonded,and preferably fusion bonded, to the shaft inner tubular member 15 anddistal tip member 24. In a method of making a balloon catheter of theinvention, the wedge-shape is formed at the distal end of the distalskirt section 21 of the balloon 19 preferably by mechanically cutting acylindrical end of the skirt section, although it may alternatively beformed by a variety of suitable methods including other methods ofmaterial removal such as laser cutting. Prior to being bonded to thecatheter shaft, the balloon distal skirt section 21 is a tubular memberwith the wedge-shaped distal end having a lumen therein configured toreceive the catheter shaft therein and the wedge-shaped distal leadingface defines a tapering port in the distal end of the balloon distalskirt section 21, so that the distal skirt section can be placed insurrounding relation to the shaft and subsequently bonded thereto. In apresently preferred embodiment, the bond extends from a location distalto the proximal end of the distal skirt section 21 to the distal end ofthe distal skirt section 21 (i.e., to the distal end 23 of thewedge-shaped distal leading face in the embodiment of FIG. 1). Thus, inone embodiment, a proximal part of the distal skirt section 21 is notbonded to the inner tubular member 15.

Although illustrated in FIG. 1 with sharp straight edges for ease ofillustration, it should be understood that during bonding of the balloondistal skirt section 21 to the distal end of the shaft, the polymericmaterials typically melt or soften, and flow. As a result, the outersurface of the balloon distal skirt section 21 typically tapers distallyto a smaller outer diameter along the length of the bond. For example,in a presently preferred embodiment, a mandrel is placed in the innerlumen of the shaft, and a heat shrink sleeve is provided on the outersurface of the wedge-shaped distal skirt section 21. Heat is applied toa distal length thereof to bond the sheath and tip together, causing thepolymeric materials of the outer sheath and distal tip to flow distallyas the members are forced down onto the mandrel. Therefore, althoughillustrated in FIG. 1 with straight outer surfaces parallel to thelongitudinal axis of the shaft and sharply terminating ends, it shouldbe understood that the outer surface of the wedge-shaped distal skirtsection 21 and distal tip 24 typically taper distally along theheated/bonded lengths thereof to a smaller outer diameter. FIG. 1therefore illustrates the balloon catheter either prior to heat fusionbonding the distal skirt section 21 of the balloon to the inner tubularmember 15 and distal tip member 24 in which the polymeric materials arecaused to flow distally during fusion bonding, or with the distal skirtsection 21 adhesively bonded to the inner tubular member 15 and distaltip member 24 so that the polymeric materials are not caused to flowdistally during bonding. FIG. 6 illustrates an embodiment having theouter surface of the wedge-shaped distal skirt section 21 and distal tip24 tapering distally along the heated/bonded lengths thereof. The fusionbonded portion 26 of the distal skirt section 21 has a tapered outer andinner surface forming a distally decreasing wall thickness. A non-bondedportion 27 is proximal to the bonded portion 26 and is not bonded to theunderlying section of the inner tubular member 15. The length of bondedportion 26 is typically about 60 to about 80% of the length of theballoon distal skirt section 21.

Preferably, the wedge-shape of the distal leading face of the distalskirt section 21 is still present after bonding, albeit with a smoother,more gradual transition from the distal skirt section 21 to the distaltip 24 due to the tapering outer surfaces. In a presently preferredembodiment, the angle of the wedge-shaped distal leading face of thedistal skirt section 21 does not change as a result of the fusionbonding process.

FIG. 7 illustrates a longitudinal cross section of an alternativeembodiment, in which the wedge-shaped outer sheath of balloon catheter10 is a wedge-shaped outer sleeve member 40 (instead of the wedge-shapedballoon distal skirt section 21 of the embodiment of FIG. 1). In theembodiment of FIG. 7, the balloon 19 has a cylindrical distal skirtsection 41 with a squared-off distal leading face abutting the proximalend of the wedge-shaped outer sleeve member 40. Similar to theembodiment of FIG. 1, the wedge-shaped outer sleeve member 40 has atapered distal leading face forming the wedge-shape of the outer sleevemember 40 which tapers at an angle relative to the longitudinal axis ofthe shaft.

In the embodiment of FIG. 7, the distal end of the shaft is locatedproximal to the distal end of the wedge-shaped outer sleeve member 40.The soft tip member 24 of the embodiment of FIG. 1 is omitted, so thatinner tubular member 15 forms the distal end of the shaft. In theembodiment of the FIG. 7, the distal end of the inner tubular member 15extends from a location proximal of the proximal end 42 of thewedge-shaped distal leading face, to a location proximal of the distalend 43 of the wedge-shaped distal leading face (i.e., the distal end ofthe inner tubular member 15 is located between the proximal and distalends 42, 43 of the wedge-shaped distal leading face of the outer sleevemember 40), so that only part of the distal end of the inner tubularmember extends through the angled end of the wedge-shaped outer sleevemember 40. With the distal end of the inner tubular member locatedbetween the proximal and distal ends 42, 43 of the wedge-shaped distalleading face, the distal end of the inner tubular member 15 is supportedby the outer sleeve member 40 but is only partially surrounded by it.However, as discussed above in relation to the embodiment of FIG. 1, thedistal end of the wedge-shaped outer sleeve member 40 can be located ina variety of alternative longitudinal positions relative to the distalend of the inner tubular member 15 in alternative embodiments. Forexample, in one embodiment, the distal end of the inner tubular member15 is at the distal end 43 of the wedge-shaped outer sleeve member 40(i.e., the distal end of the inner tubular member 15 is slightly distalto its location in FIG. 7), so that the distal ends are radiallyaligned.

The outer sleeve member 40 and balloon distal skirt section 41 aresecured to the inner tubular member 15as discussed above in relation tothe embodiment of FIG. 1. The outer sleeve member 40 is typically fusionbonded to the inner tubular member 15, although it may alternatively beformed of a heat shrink polymeric material and heat shrunk down onto theinner tubular member 15.

Outer sleeve member 40 typically has a length of about 1 to about 3 mm.The length and angle of the wedge-shaped distal leading face of theouter sleeve member 40 are similar to those of the wedge-shaped distalleading face of the distal skirt section 21 of the embodiment of FIG. 1.Similarly, although illustrated with sharp, nontapering outer surfacesin FIG. 7, it should be understood that the outer sleeve member 40and/or balloon distal skirt section 41 will typically have taperingouter surfaces after heat bonding the balloon 19 and sleeve member 40 tothe inner tubular member 15, as discussed above in relation to theembodiment of FIG. 1. Additionally, although not illustrated, a distaltip member such as tip member 24 may be provided in the embodimenthaving a wedge-shaped outer sleeve member 40, as for example with a tipmember (not shown) butt-joined to the distal end of the inner tubularmember 15 with wedge-shaped outer sleeve member 40 sealingly surroundingthe butt joint.

To the extent not previously discussed herein, the various cathetercomponents may be formed and joined by conventional materials andmethods. For example, inner tubular member 15 can be formed byconventional techniques, such as by extruding and necking materialsfound useful in intravascular catheters such a polyethylene, polyvinylchloride, polyesters, polyamides, polyimides, polyurethanes, andcomposite materials, and is preferably a multilayered tubular member.Additionally, although not illustrated, coiled or braided reinforcementsmay be included in the shaft at various locations, as is conventionallyknown.

The length of the dilatation catheter 10 is generally about 108 to about200 centimeters, preferably about 137 to about 145 centimeters, andtypically about 140 centimeters for PTCA. The outer tubular member 14distal section has an outer diameter (OD) of about 0.028 to about 0.036inch (0.70–0.91 mm), and an inner diameter (ID) of about 0.024 to about0.035 inch (0.60–0.89 mm), and the outer tubular member 14 proximalsection has an OD of about 0.017 to about 0.034 inch (0.43–0.87 mm), andan inner diameter (ID) of about 0.012 to about 0.022 inch (0.30–0.56mm). The inner tubular member 15 has an OD of about 0.017 to about 0.026inch (0.43–0.66 mm), and an ID of about 0.015 to about 0.018 inch(0.38–0.46 mm) depending on the diameter of the guidewire to be usedwith the catheter. The balloon 19 has a length of about 8 mm to about 40mm, and an inflated working diameter of about 1.5 mm to about 5 mm.

While the present invention has been described herein in terms ofcertain preferred embodiments, those skilled in the art will recognizethat modifications and improvements may be made without departing fromthe scope of the invention. For example, although the catheter 10illustrated in the Figures is an over-the-wire balloon catheter, thecatheter of the invention may be a variety of suitable ballooncatheters, including rapid exchange type balloon catheters having aguidewire proximal port located distal to the proximal end of the shaft,a guidewire distal port in the distal end of the shaft, and a relativelyshort guidewire lumen extending therebetween. While discussed primarilyin terms of a wedge-shaped distal skirt section, it should be understoodthat the balloon may have a wedge-shaped proximal skirt section orsleeve member. While individual features of one embodiment of theinvention may be discussed or shown in the drawings of the oneembodiment and not in other embodiments, it should be apparent thatindividual features of one embodiment may be combined with one or morefeatures of another embodiment or features from a plurality ofembodiments.

1. A balloon catheter, comprising: a) an elongated shaft having aproximal end, a distal end, a longitudinal axis, and at least one lumen,a distal portion of the shaft being within an outer sheath, the outersheath having a wedge-shaped distal end with an angled distal leadingface, and the distal portion of the shaft extends distally at least inpart out the distal leading face, so that the distal leading faceextends partially around the shaft circumference by an amount is greaterthan 0° and less than 360° when viewed in a cross-sectional planeperpendicular to the longitudinal axis of the shaft and which decreasesdistally toward a distal end of the distal leading face, and the distalend of the shaft is distal to at least part of the distal leading face;and b) an inflatable balloon sealingly secured to a distal shaftsection, having an inflatable interior in fluid communication with theat least one lumen of the shaft such that the wedge-shaped distal end ofthe outer sheath is located distal to the inflatable interior of theballoon wherein the outer sheath is a distal skirt section of theballoon, having at least a portion bonded to the shaft.
 2. The catheterof claim 1 wherein the shaft has a distal tip member forming the distalend of the shaft.
 3. The catheter of claim 1 wherein the at least onelumen of the shaft is an inflation lumen, and the shaft comprises anouter tubular member defining the inflation lumen, and an inner tubularmember defining at least a portion of a guidewire receiving lumen. 4.The catheter of claim 3 wherein the shaft includes a distal tip memberhaving at least a portion distal to the inner tubular member, anddefining a distal portion of the guidewire lumen in fluid communicationwith the portion of the guidewire lumen defined by the inner tubularmember, and the distal tip member forms the distal end of the shaft. 5.The catheter of claim 1 wherein the outer sheath wedge-shaped distalleading face is oriented at an angle of about 30 to about 60 degreesrelative to the longitudinal axis of the shaft.
 6. The catheter of claim1 wherein the outer sheath wedge-shaped distal leading face has aproximal end and a length of about 2.5 to about 4 mm extending from theproximal to the distal end thereof, and the outer sheath has acylindrical section proximal to the wedge-shaped distal leading face. 7.The catheter of claim 6 wherein the length of the wedge-shaped distalleading face is about 20 to about 75% of the length of the outer sheath.8. The catheter of claim 6 wherein the distal end of the shaft islocated distal to the distal end of the wedge-shaped distal leadingface.
 9. A balloon catheter, comprising: a) an elongated shaft having aproximal end, a distal end, an inflation lumen, and a guidewirereceiving lumen; and b) an inflatable balloon sealingly secured to adistal shaft section, having an interior in fluid communication with theinflation lumen, and having a distal skirt section bonded to a distalportion of the shaft, the distal skirt section having an angled distalleading face, and the distal portion of the shaft extending distally atleast in part out the distal leading face so that the distal leadingface extends partially around the shaft circumference by an amount whichis greater than 0° and less than 360° when viewed in a cross-sectionalplane perpendicular to the longitudinal axis of the shaft and whichdecreases distally toward a distal end of the distal leading face, andthe distal end of the shaft is distal to at least part of the angleddistal leading face.
 10. The catheter of claim 9 wherein the shaftcomprises an outer tubular member defining the inflation lumen, and aninner tubular member in at least a distal portion of the inflation lumendefining at least a portion of a guidewire receiving lumen, and theballoon distal skirt section surrounds the inner tubular member.
 11. Thecatheter of claim 10 wherein the shaft includes a distal tip memberforming the distal portion of the shaft, the distal tip member having atleast a portion distal to the inner tubular member and defining a distalportion of the guidewire lumen in fluid communication with the portionof the guidewire lumen defined by the inner tubular member.
 12. Thecatheter of claim 11 wherein the balloon distal skirt section sealinglysurrounds the distal end of the inner tubular member and at least theproximal end of the distal tip member.
 13. The catheter of claim 11wherein the distal end of the distal skirt section forms a wedge-shapeddistal leading face oriented at an angle of about 30 to about 60 degreesrelative to a longitudinal axis of the inner tubular member.
 14. Thecatheter of claim 13 wherein the distal tip member extends from proximalof the wedge-shaped distal leading face to distal of the wedge-shapeddistal leading face.
 15. The catheter of claim 13 wherein the distal tipmember is spaced distally from the distal end of the inner tubularmember forming a gap therebetween, and the balloon distal skirt sectionsurrounds the gap.
 16. The catheter of claim 15 wherein an outer surfaceof the balloon distal skirt section bonded to the inner tubular memberand to the distal tip member tapers distally to a smaller outerdiameter.